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Home >> Cadillac >> 2018 >> Escalade Base, 4WD >> Repair and Diagnosis >> External Pages >> Different car >> Section 16 (Transfer Case - Mp 3010 (NP0)) >> Diagnostic Information And Procedures >> DTC P185F, P279A, P279B, P279C: Transfer Case/Four Wheel Drive (4WD) Neutral Range >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2018 GMC Yukon XL, 2018 GMC Yukon, 2018 Chevrolet Tahoe, and 2018 Chevrolet Suburban. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition ON/Vehicle in Service Mode
  2. Clear All Vehicle DTCs.
  3. Operate the vehicle within the Conditions for Running the DTC.
  4. Verify the DTC does not set.
  5. Verify the scan tool parameter:4WD Low SignalDisabled
    • If the parameter does not display the following:Disabled 

      Test or replace the component:Transfer Case Assembly

    • Go to next step: If the parameter displays the following: =Disabled 
  6. Program the ECM.
  7. Operate the component:S77 Transfer Case Shift Control Switch - 4WD High/Locked
  8. Operate the vehicle within the Conditions for Running the DTC.
  9. Verify the DTC does not set.
    • If the DTC sets 

      Replace the component:K20 Engine Control Module

    • Go to next step: If the DTC does not set 
  10. Operate the component:S77 Transfer Case Shift Control Switch - 4WD Low
  11. Operate the vehicle within the Conditions for Running the DTC.
  12. Verify the DTC does not set.
    • If the DTC sets 

      Replace the component:K20 Engine Control Module

    • Go to next step: If the DTC does not set 
  13. Operate the component:S77 Transfer Case Shift Control Switch - Neutral
  14. Operate the vehicle within the Conditions for Running the DTC.
  15. Verify the DTC does not set.
    • If the DTC sets 

      Replace the component:K20 Engine Control Module

    • Go to next step: If the DTC does not set 
  16. All OK.
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